#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <vector>
#include <cstring>
#include <cctype>
#include <algorithm>
using namespace std;

#ifdef INFOARENA
#define ProblemName "fractii"
#endif

#define MCONCAT(A, B) A B
#ifdef ProblemName
#define InFile MCONCAT(ProblemName, ".in")
#define OuFile MCONCAT(ProblemName, ".out")
#else
#define InFile "fis.in"
#define OuFile "fis.out"
#endif
typedef long long LL;

#define MAXN 1000010
int a[MAXN];

int main() {
	assert(freopen(InFile, "r", stdin));
	assert(freopen(OuFile, "w", stdout));
	int N;
	scanf("%d", &N);
	LL ans = 1LL;
	for (int i = 1; i <= N; ++i)
		a[i] = i - 1;
	for (int i = 2; i <= N; ++i) {
		ans += 2 * a[i];
		for (int j = i + i; j <= N; j += i)
			a[j] -= a[i];
	}
	printf("%lld\n", ans);
	return 0;
}